If you want, you can ask for the resources (time / payment) to this the right way – to (carefully) replicate the environment and test things out so you know exactly what you are doing.
If this is denied then, as an engineer, i would not want to touch it.
Dan
p.s. And, even replicating might be non-trivial – do you know all system parts?
There’s at least one typo in there. 
Also, the “.pl” extensions s aren’t needed (usually).
Which version of swipl are you running? (You can find out by: swipl --version)
I would never touch a running production server that I’ve never used, without setting up a test server somewhere else and trying out my changes on it. There is no such thing as a “trivial” change in production. (This is based on ~40 years of experience.)
I entered the typo when I changed the names of the files for privacy.
The version is 8.2.4 for x86_64-linux
I again thank you all from the bottom of my heart but I already started the procedure to reject the task. I really understood like 2% of all you kind people wrote in this thread and I’m obviously too out of touch on the matter to do anything good, given the short time I had. For one last time I thank you all again for your support but I’m out. In fact, I think I was never in.
Tara,
Perhaps, one good think might come out of this – perhaps Prolog can pique or interest.
It surely is a unique language, that can prove highly productive in production as well.
There likely is a reason why that system was written in Prolog …
Dan